High-pressure pump



Nov. 7, 1950 F. H. CAREY HIGH-PRESSURE PUMP Filed June 14, 1948 l'figfi 1 4 W fl a a E w I: E E f Inventor fl. carely, Artur/117 I g I Patented Nov. 7, 1950 HIGH-PRESSURE PUMP Frederick Henry Carey, Cheltenham, England,

assignor to Dowty quipment Limited, Clieltenham, England Application June 14, 1948, Serial No. 32,760 In Great Britain June 24, 1947 8 Claims.

This invention relates to high pressure pumps in which a plunger is constrained to reciprocate with respect to its bore by some controlling member such, for example, as a track ring, if the pump be of the radial cylinder rotating type, or a swash plate or equivalent controlling member if the pump be of the swash plate type. In either event the outer ends of the plungers are provided with slippers or some equivalent anti-friction members which engage the track ring or the swash plate, but whatever precautions are taken to minimize friction the fact remains that with such pumps operating at high pressure there is inevitably a drag effect at the slippers or equivalent bearing members which tends to tilt the plungers in relation to their bores and the effect is to produce areas where the friction is high at or near the outer end of the plunger bores at what may be conveniently called the trailing edge of the plunger and another at or near the inner end of the plungers at what may conveniently be called the leading edge with respect to the direction of travel. The high frictional loading at these points tends to cause localized wear possibly eventually resulting in the plungers picking up with respect to the bore or eventually even leading to seizure in extreme cases. The efiect is in creased the higher the working pressures become and if the pump is to be effective at high pressures the plungers must be an exceptionally good fit in the bores and lubrication is difiicult. Yet again the pump may be required to operate the fluids which possess little or no real lubricating properties.

It is an object of the invention to balance out the drag loading and to that end fluid pressure is applied against the plunger at a localized area in which the fluid pressure operates to oppose the tendency of the plunger to tilt with respect to its bore under the influence of the drag loading.

It will be obvious that the drag loading is of major importance on the delivery stroke of each plunger and may be of comparatively little significance on the suction stroke because on the delivery stroke the plungers are forced outwardly by the full output pressure of the pump and it therefore will sufiice in most cases to apply the drag load balance reaction only on the delivery stroke.

In order that the invention may be clearly understood and readily carried into effect one embodiment will now be described by way of example with reference to the accompanying drawings, of which:

Figure 1 is a sectional side elevation on the line I-I in Figure 2;

Figure 2 is a sectional end elevation on the line IIII in Figure 1;

Figure 3 is a fragmentary detail shown in development; and

Figure 4 is a sectional elevation showing a modification of a detail.

The pump shown has a stationary casing I I to which is secured eccentrically by bolts l2 a ported valve spindle I3 having suction and outlet ports 14 and I5 respectively. A bushed radial cylinder assembly or star member I6 having'seven (or other desired number of) cylinder bores 20 is driven to rotate about the valve spindle I3 by a drive shaft I! which is coupled to the cylinder A plunger I 9 is reciprocable in each radial cylinder 20 and has at its outer end a slipper bearing member 2| which operates on the principle of a Michel pad bearing with respect to a track ring 22 secured in the easing II. The strokes of the plungers l9 are determined by the eccentricity of the track ring 22 in relation to the axis of the valve spindle .l3. Liquid, which may be petrol, parafiin or other liquid having low or negligible lubricating properties may be supplied through a primary inlet port (not shown) leading into the space within the casing ll somewhere near the inner part of the cylinder'assembly. The incoming liquid is.

centrifuged outwardly towards the track ring 22 to pass through a primary outlet port 26 in the track ring 22 where it is transferred through a transfer passage 21 into the suction port It. The outward movements of the plungers as they revolve across the suction port I 4 suck the liquid into the corresponding cylinders and eventually discharge the liquid into the outlet port l5 from which it passes into a supply conduit (not shown).

The cylinder assembly rotates in the direction indicated by the arrow in Figure 2, and it will be appreciated that the inevitable drag effect at the slipper bearing members tends to tilt the plungers in relation to their bores and the effect is to produce areas where the friction is high at or near the outer ends of the plungers at what may conveniently be called the trailing edges 28 of the plungers and others at or near the inner ends of the plungers at what may conveniently be called the leading edges 29. The high frictional loading at these points tends to cause localized wear which may result in the plungers picking up with respect to the bores and possibly to seizure in extreme cases. Drag loading is of major importance during the delivery strokes when there is increased pressure between the bearing pads and the track ring with correspondingly increased tendency for the plungers to tilt and, in order to overcome this, each plunger I9 is formed from its inner face with a passage 30 extending from the inner face and opening near the inner end of the plunger at the leading edge of the plunger. During the delivery stroke the high pressure developed in the liquid reacts between the plunger and its cylinder to counteract the tendency for the plunger to tilt. The higher the pressure developed, the greater is the drag loading at the slipper bearing member with greater tendency for the plunger to 'tilt under the effect of this drag loading, and the, greater is the reaction applied to counter this tilting tendency.

If desired, a drag load reaction force may also be applied against the plungers near their outer ends and for this purpose the star member l6 has for each cylinder a passage 3| leading from near the outer end of the cylinder adjacent the trailing edge of the plunger and opening into the inner end of the cylinder. For convenience of production, the part 32 of the passage is formed as a groove in the outer surface of the bush and this groove opens into the'hole 33 in the bush which, when the bush is locked in position within the star member, registers with the cylinder bore. A part of the bush-is.

shown in development in Figure 3. In the same 'way as pressure of liquid counters tilting-in one sense through the passage 39, so it counters tilting inv the opposite sensethrough the pas sage 3|. a

In the example shown, each slipper pad '2l bears against the corresponding plunger l9 through a pin 34 and a universal element 35 and in order to maintain the rubbing surfaces moistened during operation of the pump, a duct 36 extends through the universal element 35 and through the plunger I!) to open at the trail- I ,ing edge of the plunger. During reciprocation of the plunger the duct 38 momentarily registers with the passage 3| to allow a very small quantity of liquid to reach the rubbing surfaces.

As .an alternative to the passages 3| in the star member leadingto the outer ends of the 7 cylinder bores, the plungers may each be formed,

see Figure 4, with a branch passage 31 extending up from the passage 30 so that drag load balance reaction forces wil1 be applied at the inner and outer parts of the plungers at the leading and trailing edges respectively. These forces will of course come into effect only upon the delivery strokes of the plungers.

Thematerial of the plunger and/or the bore may be locally relieved at the point or'points where the fluid pressure is required to operate and it will be understood that in basic design the relieved areas may be chosen having regard to the output pressure at which the pump is required to operate to give just the required degree of balance in relation to the prevailing drag loads.

In some cases it may be desirable for the drag load balance reaction forces to be applied at all i times, and to this end fluid passages leading to either or both of the inner and outer ends of sists in balancing the rotor, or star member l8.

I claim: 1. In a pum of the type which comprises a cylinder assembly the .bores whereof are arranged about a common axis, a plunger reciprocable within each-bore, a controlling surface offset differently relative to each of the several plungers, and a slipper interposed between each plunger and said controlling surface, the conof the plungers, and tending to create maximum wear in localized areas between each plunger and its bore by reason of the tendency of the plunger to cock in its bore under the influence of drag loading between the slipper and the controlling surface; and a passage leading from a pressurized pump space to such localized areas, during maximum drag loading on the latter, the pressure fluid so conveyed reacting there between the plunger and its bore to oppose the cocking tendency of the plunger.

2. A pump as set forth in claim 1, characterized in that passages individual to each plunger and bore are formed in a pump element which is one of the relatively movable elements, and by such relative movement each passage is cyclically placed in communication with the pressurized space during its plungers delivery stroke, and is relieved of such communication during its plungers suction stroke.

3. A pump as set forth in claim 1, characterized in that passages communicate with the clearance space between each plunger and its bore, at two points only, namely, at the inner end of the plunger at its leading edge, and at the outer end of the plunger at its trailing edge.

4. A pump as set forth in claim 1, characterized in that the passage is formed in the cylinder assembly and terminates adjacent one end of the plunger, to be masked by the latter substantially throughout its stroke.

5. A pump as set forth in claim 4, including a duct in the plunger leading to its slipperbearing, and located to register with the outlet of the passage in the cylinder assembly at the start of each delivery stroke,

6. A pump as set forth in claim 1, characterized in that a passage extends from the inner end of each cylinder, and is pressurized only during delivery stroke.

7. A pump as set forth in claim 1, wherein the cylinder assembly is rotative and the bores are arranged radially therein, and the controlling surface is formed as a. circular track ring eccentric to said rotative cylinder assembly, a central spindle about which the cylinder assembly rotates, and characterized in that the passages lead to the leading and trailing edges of each plunger, at the inner and outer ends thereof, respectively.

8. A pump as set forth in claim 7, including additionally annular channels formed in the clearance space between the spindle and the rotative cylinder assembly.

FREDERICK HENRY CAREY.

REFERENCES CITED The following references, are of record in the file of this patent:

UNITED STATES PATENT Number Name Date 580,838 Almond Apr. 20, 1897 1,064,542 Rittersbach June 10, 1913 1,679,964 Edwards Aug. 7, 1928 2,025,758 Long Dec. 31, 1935 2,155,455 Thoma Apr. 25, 1939 FOREIGN PATENTS Number Country Date 194,959 Great Britain 1923 

